The present invention relates to a device for uniformly spreading powdery materials over a circular surface with the aid of a distribution chute suspended in a pivoting manner from a rotary cage and whose angle of tilt in relation to the vertical axis of the said cage is adjustable.
A device of this kind is proposed by document EP-A-0,343,466. Although not limited thereby, the present invention aims more particularly at the application of this known device for distributing lignite powder in a fluidized-bed lignite drier. In this application, the device for driving the chute has to meet two criteria which are mutually reconcilable only with difficulty. On the one hand, it is necessary at all costs to avoid the penetration of oil or of lubricant into the enclosure of the drier. On the other hand, the design of a conventional drive mechanism, for example, a gear driven mechanism, is difficult to conceive without lubrication if one desires to avoid the risk of seizing due to the deleterious action of fine particles of lignite powder.